Field of the Invention
The present invention relates to an image reading apparatus configured to read an image on a sheet, and an image forming apparatus equipped with the image reading apparatus.
Description of the Related Art
Heretofore, image forming apparatuses such as copying machines and facsimiles having image reading apparatuses configured to optically read images on documents are known. This type of image reading apparatus is equipped with an automatic document conveying apparatus (Auto Document Feeder, hereinafter referred to as ADF) configured to convey one sheet of document at a time, and a scanner unit configured to read the image on the document being conveyed through a platen glass.
If a foreign substance adheres to a surface of the platen glass, light emitted from the scanner unit is blocked by the foreign substance, and linear image noises (hereinafter referred to as “image streaks”) may be formed on the image information being read. Examples of such foreign substances include paper dust generated from documents or shavings of conveyance rollers formed to convey documents. Therefore, an arrangement is known where platen glass is electrically grounded to relieve electrostatic attraction operating between the foreign substance and the platen glass, and a leading edge of the document being conveyed scrapes the foreign substance adhered to the platen glass to thereby clean the platen glass.
Meanwhile, some type of image reading apparatuses includes two scanner units corresponding to front and rear sides of the document, and image information is acquired from both sides of the document while the document is being conveyed once by the ADF. Even in such image reading apparatus, if foreign substances are adhered to the platen glass opposed to the rear side of the document, image streaks may occur to the image information being read.
Therefore, Japanese Unexamined Patent Application Publication No. 2012-70126 proposes, as illustrated in FIG. 11, an image reading apparatus including a reading sensor 13 configured to read image information on a rear side of a document through a platen glass 12, and a shaft member 53 arranged to face the reading sensor 13 and equipped with a cleaning brush. According to the image reading apparatus, the shaft member 53 rotates to cause a cleaning brush 54 to clean foreign substances adhered to the platen glass 12, thereby preventing generation of image streaks.
However, the image reading apparatus taught in Japanese Unexamined Patent Application Publication No. 2012-70126 can remove the foreign substances adhered to a side, constituting the conveyance path, of the platen glass 12, but it cannot remove the foreign substances floating between the platen glass 12 and the reading sensor 13. Therefore, image streaks occur in a state where foreign substances enter between the platen glass 12 and the reading sensor 13, and there is fear that the document may not be read preferably.
Moreover, in order to read the image information of the document highly accurately, the document must be conveyed in a state where a leading edge of the document is in parallel with an image reading line of the reading sensor 13. However, there may be a case where the image reading line of the reading sensor 13 and the leading edge position of the document are deviated, due to intersection of components, for example, and in that case, it was necessary to adjust the position of the reading sensor 13.